GATE 2016- ADMISSION IN THE DEPARTMENT OF OCEAN ENGINEERING AND NAVAL ARCHITECTURE

Ocean Engineering and Naval Architecture (commonly known as OENA) course are basically offered by IIT Kharagpur and IIT Madras. The programe offered by these two IIT's are B tech, Dual degree, M Tech and MS by Research (not in IIT Kharagpur).

The above mentioned branch basically involves the study of ships and offshore structures.

Admission in B tech and Dual degree are offered on the basis of JEE scorecard where as admission in M tech and MS are offered through GATE score card.

M tech admission can be attained with all India GATE percentile anywhere between 98.5 to 99 %, MS admission also required the above mentioned percentile along with the grilling interview. 

 M tech is two years program whereas MS by research can be completed anywhere between 2.5 years to 3 years. Completing MS within 2 years is bit tough task specially in IIT Madras due to intense quality of research.

WHAT TO EXPECT FROM THESE COURSES:

1: Good understanding of ships, coastal structures (like break waters) and offshore structures;

2: Interaction with high end development of offshore technologies for renewable energies like wind, wave and tidal energies.

3: Expertise in Computational Fluid Dynamics and Finite element. Both the above mentioned IIT's are well equipped with the facility and faculty which can be exploited to attain these higher end knowledge.

INTRODUCTION TO ADDED MASS FOR OFFSHORE STRUCTURES

In case of unsteady motion of bodies underwater or unsteady flow around objects, we must consider an additional effect (force) acting on the structure when formulating the system equation.

A typical mass-spring-dashpot system can be described by the following equation:

  mx˙˙ + bx˙ + kx = f (t )

where m is the system mass, b is the linear damping coefficient, k is the spring coefficient, f(t) is a driving force acting on the mass, and x is the displacement of the mass. The natural frequency ω of the system is simply:

w=SQRT(k/m):                                                                                          1.1

Given an object of mass m attached to a spring, you can determine the spring constant by
setting the mass in motion and observing the frequency of oscillation, then using equation
(1.1) to solve for k. Alternately we can also determine the spring coefficient k by simply
applying a force f and measuring the displacement x:
                                                                                     f = kx

The apparent mass of an object in air differs from the apparent mass of an object in water.
Statically, the buoyancy force acting on the body makes it appear less massive. Using a
load (force) cell to measure the weight Mg of an object will reveal this disparity quite
clearly. It is important to take this into account when formulating the natural frequency
of a spring-mass system in water. In this lab we will compare the natural frequency of
such a spring-mass system in air and in water. In addition to the buoyancy effect, an
added mass term must be considered.
In a physical sense, this added mass is the weight added to a system due to the fact that an
accelerating or decelerating body must move some
volume of surrounding fluid with it as it moves. The added mass force opposes the
motion and can be factored into the system equation as follows:

  mx˙˙ + bx˙ + kx = f (t )-ma x˙˙

where ma is the added mass. Reordering the terms the system equation becomes:
  (m+ma )x˙˙ + bx˙ + kx = f (t )
From here we can treat this again as a simple spring-mass-dashpot system with a new
mass a
                                                    m'= m+ ma
                                      such that the natural frequency of the system is now
                                                   
                                                    w=SQRT(k/m+ma):

Software useful for Offshore and Ocean Engineering

Software useful for offshore and ocean engineering:

The basic software used for solving offshore and naval architecture are as follows:

Ansys AQWA:

Ansys AQWA is capable of handling both offshore and marine structures. The analysis can be carried out in both frequency and time domain. The software is also capable of designing mooring lines. It has got the best animation features available till date.

ANSYS® AQWA™ is a commercial hydrodynamic package capable of solving the complex wave body interaction problem in the frequency domain.

Fluid structure interaction problems are solved using three dimensional Boundary Integral Equations

Method(BIEM). 

BIEM is popularly known as panel method and solves the hydrodynamic radiation and diffraction problem of floating structure interaction with waves (wave body interaction). 

The concept involves the solution of the Laplace equation in the fluid domain. The solution procedure basically consists of boundary value problem which requires the application of boundary conditions to solve a desired set of equations, from which velocity potentials are obtained.

SIMULATION USING ANSYS® AQWA™

The programs within the AQWA suite are as follows:

AQWA-LINE: The core solver where 3-D diffraction & radiation analysis of the

modeled structure is carried out and wave forces and response of the structure are calculated. AQWA-LINE also check the hydrostatic stability of the model. It is capable of solving both first order and second order forces in the frequency domain.

For small bodies or structures that are drag dominated, the nonlinear drag force is discarded while using this suite.

AQWA-LIBRIUM: This suite is used to calculate the static equilibrium position and unbalanced force on the structure. AQWA-LIBRIUM is capable of performing the static calculation for free floating as well as moored body.

AQWA-FER: This module is efficient to compute the spectral analysis of coupled or uncoupled response of the floating system. The analysis can be channeled out for both regular and random waves.

AQWA-NAUT: This suite is a time domain solver capable of capturing real time

nonlinear response of free floating and moored body including coupling effects.

More information on ANSYS AQWA can be obtained by clicking here;

https://www.youtube.com/user/utk910